Cosworth Vegas had two fuel pumps - a low pressure pump inside the fuel tank that ensured fuel was supplied to high pressure pump located under the car below the passenger rear seat. Suitable low pressure pumps can still be found. The high pressure pumps have been unavailable for many years and typically owners send them to Fuel Injection specialty shops to be rebuilt.

A common modification the last 10 years are so is to replace the in-tank pump with a fuel pump from an 80' vintage V6 Camaro. And eliminate the high pressure pump altogether. I have one car modified like this and will be doing a second car in the near future. Obviously, if you are looking to maintain originality, this is not the best option. A write up of how to do this is in one of the older Cosworth Vega magazines.

I am not aware of availability of a correct pressure regulator. I would recommend reaching out to other members to locate a used original.